Influence of extrusion temperature on dynamic deformation behaviors and mechanical properties of Mg-8Al-0.5Zn-0.2Mn-0.3Ca-0.2Y alloy

This study demonstrates that the dynamic recrystallization (DRX) and dynamic precipitation (DP) behaviors and resultant mechanical properties of the recently developed nonflammable AZXW8000 alloy vary significantly with the extrusion temperature. With an increase in the extrusion temperature from 250 to 350 °C, the DRX behavior of the alloy improves through the transition of dominant recrystallization mechanisms from twinning-induced DRX and continuous DRX to discontinuous DRX, which causes an increase in the DRX fraction of the extruded alloy. During extrusion at 250 °C, continuous Mg17Al12 precipitates, which are statically formed during preheating before extrusion, fully dissolve into the matrix and numerous fine Mg17Al12 precipitates are formed dynamically throughout the material. These fine precipitates refine the dynamic recrystallized (DRXed) grains through grain-boundary pinning. As a result, the nonflammable AZXW8000 alloy extruded at 250 °C exhibits a high yield strength of 307 MPa and an ultimate tensile strength of 398 MPa. The tensile strength of the extruded alloy decreases with increasing extrusion temperature, which is attributed primarily to significant weakening of the precipitation hardening and strain hardening effects. However, the tensile ductility improves with increasing extrusion temperature owing to a decrease in the amounts of precipitates and unDRXed grains. © 2019 The Authors.